1. Field of the Invention
The present invention relates to cranes and more particularly relates to attachments for modifying a normal duty crane to a heavy duty crane to provide a maximum diameter support base at minimum cost while at the same time minimizing the time required for set up and strip down.
2. Description of Prior Art
It is well known in the art to modify a standard crane into a heavy duty crane by providing a large diameter load supporting ring which reduces the load applied on the bearings between the upper works and the lower works. However, these prior art cranes are unnecessarily heavy and expensive, and require very wide paths for movement from place to place if the load supporting ring is to remain assembled on the machine. Many of these prior art heavy duty cranes require considerable set up and strip down time when operating at and moving between several working sites.
One prior art heavy duty crane is disclosed in assignees' United States Dvorsky et al Patent Appln. Ser. No. 847,639 (now U.S. Pat. No. 4,196,816 dated Apr. 8, 1980) which operates quite satisfactorily but requires considerable set up and strip down time at each site, and also requires a path wide enough to accommodate a large diameter full depth ring when moving from site to site.
The Dvorsky et al crane includes an auxiliary frame that is supported by a ring and engaged by the upper works of the crane for rotation therewith on the ring. Rollers on the front and rear ends of the auxiliary frame ride along the upper surface of the ring, which is full depth. A plurality of vertically adjustable standards support the ring in horizontal operative position. It will be appreciated that considerable time and manual effort is required to set up, and after the work has been completed at a particular site, to strip down the crane so that it can be moved from one site to another site. The strip down procedure involves operating the four hydraulic cylinders to lift each of the adjustable standards above the ground, and then manually screwing each standard up a sufficient distance to provide road clearance prior to lowering the tracks in crane supporting position on the ground. At this time the ring, standards, and the other components are supported by the lower works.
In addition to the above operations, the strip down procedure requires using another smaller auxiliary crane to remove a sufficient amount of the counterweights from the rear end of the auxiliary frame to balance the weight of the boom and gantry acting on the forward end of the auxiliary frame. It will be appreciated that this weight balancing procedure must be performed by all of the heavy duty cranes, including the crane claimed herein, before the cranes can be safely moved to another site.
United States Beduhn et al U.S. Pat. No. 3,878,944 which issued on Apr. 22, 1975 also discloses a mobile crane which includes a large diameter ring that is secured to the lower body or works of the crane by beams parallel to and externally of the crawler assembly of the vehicle. The crane includes an upper works rotatable about a vertical axis concentric with the ring, with a boom carrier pivoted thereto for pivotally supporting the lower ends of the boom and mast above the forward portion of the ring. A counterweight carrier is also pivoted for vertical movement to the upper works for supporting counterweights above and outwardly of the rear end of the ring. Rollers on the boom carrier and counterweight carrier engage the ring to permit rotation of the carriers and parts supported thereon around the ring. The crane with the large diameter ring supported thereon is driven to its operational site and then hydraulic jacks on the ends of the ring supporting beams are lowered to lift and level the ring. Thereafter, a plurality of manual jacks on the ends of short beams that are pivoted to the vehicle frame are lowered to support the ring in its horizontal position. The crane, therefore, carries the heavy, large diameter ring from site to site thereby requiring a wide path between sites in order to accommodate the large diameter ring. Considerable time is required for set up and strip down as compared to the heavy duty cranes of the subject invention.
United States Beduhn U.S. Pat. No. 3,485,383 which issued on Dec. 23, 1969 discloses a self-propelled crane with a large diameter supporting ring rigidly secured to the lower works of the crane, and a boom carrier pivoted to the upper works and supported on the ring by rollers. The upper works is mounted for pivotal movement about a vertical axis concentric with the ring, and includes a conventional counterweight on its rear end. An auxiliary counterweight behind the conventional counterweight is provided with rollers for support on the rear portion of the ring. Jacks are provided for initially supporting and leveling the ring at an operation site; and thereafter wooden blocks, hydraulic jacks or the like are used to support the ring from the ground. This crane therefore requires considerable set up and strip down time for filling the gap between the ring and the ground with planks or the like. Also, the large diameter ring requires that the path between operation sites be quite wide unless the ring itself is dismantled from the crane prior to moving the crane to another site.
German Pat. No. 1,185,353 which issued on Sept. 9, 1965 discloses a mobile crane having lower works, and upper works mounted thereon for pivotal movement about a vertical axis. A boom and mast supporting carriage is hinged to the forward portion of the upper works and includes rollers which ride on a large diameter ring rigidly secured to the lower works. Counterweights at the rear of the upper works are pivotally supported for vertical movement by arms which are pivoted near the forward end of the boom carriage and includes intermediate rollers which ride along a small diameter ring concentric with the vertical axis. The diameter of the ring thus determines the minimum width of the path required to move the crane from site to site, and considerable set up and strip down time is required to fill the gap between the ground and the ring to support the ring in a horizontal operative position.
United States Kauffman U.S. Pat. No. 2,139,960 which issued on Dec. 13, 1938 discloses a crane which has a large diameter ring assembled around its base at a work site. The ring is supported by a plurality of bolsters and cross beams and is centered relative to the vertical axis of the crane by a plurality of adjustable spokes. The rear ends of struts support some of the load applied and are connected to the mast, and the rear ends of side bars are pivoted to the cab. The forward ends of the struts and side bars are supported by pairs of wheels for rotation along the ring during normal operation of the crane. However, the rear or counterweight portion of the crane is not supported by the ring during normal operation.
When it is desired to move the Kauffman crane to another site, the bolsters and cross beams must be removed, and the ring may be supported on the crane chassis by grapples having rollers thereon that are pivoted into ring supporting position below an annular flange on the ring. The rollers allow the cab to be rotated relative to the ring when the crane is being moved from place to place.